Our objective is to study structural and functional properties of acetylcholinesterase (AChE), acetylcholine receptor (AChR) and other identifiable excitable membrane components and to investigate their interactions with and roles in the excitable membrane. Structural distinctions between various forms of eel AChE isolated by affinity chromatography will be studied by SDS gel electrophoresis. Antibodies to AChE subunit components will be investigated. Binding studies of cholinergic ligands, neurotoxins, and Ca ions to purified soluble AChR are planned, and the essential nature of a free sulfhydryl near the AChR active site prior to disulfide reduction will be analyzed. The synthesis and interaction of fluorescent probes specific to AChE or AChR will be investigated. Membrane fragments rich in AChE and/or AChR will be isolated by affinity chromatography, and the accessibility of both proteins when membrane bound will be determined by lactoperoxidase iodination studies. Studies on the effects of veratridine on synaptic membrane and Ca ions-depletion on ion permeability will be carried out on the intact eel electroplax. These investigations will permit experimental examination of several proposals in an integral model of nerve excitability.